3Com 3C17205-US - Corp SUPERSTACK 3 SWITCH 4400 24PORT Implementation Manual page 35

Member links must retain the same groupings at both ends of an
aggregated link. For example, the configuration in
work as Switch A has one aggregated link defined whose member
links are then split between two aggregated links defined on Switches
B and C. Note that this illegal configuration could not occur if LACP is
enabled.
Figure 5 An illegal aggregated link configuration
To make this configuration work you need to have two aggregated links
defined on Switch A, one containing the member links for Switch B and
the other containing those for Switch C.
Alternatively, if Switches B and C are, for example, stacked Switch 4400
Series units and their member link ports defined as part of the same
aggregated link as shown in
correctly as aggregated links are supported stack-wide by the Switch
4400 Series.
Figure 6 A legal aggregated link configuration
When using an aggregated link, note that:
Figure 6, the configuration will operate
Aggregated Links 35
Figure 5 will not